This section introduces aspects that may help facilitate a better understanding of the inventions. Accordingly, the statements of this section are to be read in this light and are not to be understood as admissions about what is prior art or what is not prior art.
Rapidly increasing demand for mobile data applications coupled with limited licensed spectrum availability has led to significant interest in the deployment heterogeneous networks comprising mixtures of macro-cells and small cells. Often these small cells support radio access technologies that are different from those supported by macro cells. For instance, the macro cells may offer wireless access based on the 3GPP LTE standards while the small cells offer WIFI access which not only uses different frequency bands but also an entirely different air interface standard. Since a large number of users are typically connected to macro cells (which cover relatively large geographic areas), the bit rates and the overall quality of experience available to users connected to macro cells are usually lower than those available to users connected to small cells. At present, users can benefit from the presence of small cells through hard handoffs. That is, if a user connected to a macro cell is in the vicinity of a small cell, it may break its existing connection to the macro cell and establish a new connection to the nearby small cell. The quality of experience for a user can vary significantly when it hands over from a small cell to a macro cell and vice versa. Such handovers can also be disruptive to the applications that are running on the user device.
Dual Connectivity (DC), which is being standardized by 3GPP in its upcoming releases, has been proposed as a means to overcome these problems and enable user devices to opportunistically benefit from the presence of small cells with minimal disruption to their active applications. DC allows a user device to be anchored to a cell, usually a macro cell supporting the 3GPP LTE access standard, while opportunistically setting up a secondary connection to another cell, often a small cell, should it be in the vicinity of the latter. The other cell providing the secondary connection can be on the same or different frequency band as the primary cell. Also, the air interface supported by the secondary cell can be the same as that associated with the primary air interface or different from the latter. An example of the latter would be where the primary air interface is 3GPP LTE while the secondary air interface is WIFI. Dual connectivity with primary and secondary connections supported by different radio access technologies (air interfaces) is called Multi-Radio-Access-Technology Dual Connectivity or Multi-RAT DC for short. New solutions and techniques that support and improve such Multi-RAT DC operation would therefore meet a need and advance wireless communications generally.
Specific embodiments of the present invention are disclosed below with reference to FIGS. 1-5. Both the description and the illustrations have been drafted with the intent to enhance understanding. For example, the dimensions of some of the figure elements may be exaggerated relative to other elements, and well-known elements that are beneficial or even necessary to a commercially successful implementation may not be depicted so that a less obstructed and a more clear presentation of embodiments may be achieved. In addition, although the logic flow diagrams above are described and shown with reference to specific steps performed in a specific order, some of these steps may be omitted or some of these steps may be combined, sub-divided, or reordered without departing from the scope of the claims. Thus, unless specifically indicated, the order and grouping of steps is not a limitation of other embodiments that may lie within the scope of the claims.
Simplicity and clarity in both illustration and description are sought to effectively enable a person of skill in the art to make, use, and best practice the present invention in view of what is already known in the art. One of skill in the art will appreciate that various modifications and changes may be made to the specific embodiments described below without departing from the spirit and scope of the present invention. Thus, the specification and drawings are to be regarded as illustrative and exemplary rather than restrictive or all-encompassing, and all such modifications to the specific embodiments described below are intended to be included within the scope of the present invention.